Singlet oxygen quantum yields (Φd) in water using beetroot extract and an array of LEDs

Bonacin, Juliano Alves; Engelmann, Fábio Monaro; Severino, Divinomar; Toma, Henrique E.; Baptista, Maurício da Silva

doi:10.1590/s0103-50532009000100006

Cited by 41 publications

(31 citation statements)

References 24 publications

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“…7 Dye-sensitized solar cells based on bn exhibit a remarkably high energy conversion efficiency (2.7 %) 8 for a natural dye sensitizer; two-electron dye oxidation following one-photon excitation has been recently proposed. 9 Red beet Beta vulgaris L. 10,11 as well as fruits of some cacti species of Opuntia, 12 Mammillaria 13 and Hylocereus 14 contain bn dye (100 -600 mg kg -1 in red beet).…”

Section: Introductionmentioning

confidence: 99%

Time-resolved spectroscopy of the singlet excited state of betanin in aqueous and alcoholic solutions

Wendel

Niziński

Tuwalska

et al. 2015

Phys. Chem. Chem. Phys.

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The photophysical properties of betanin in aqueous and alcoholic solutions were determined at room temperature using ultrafast UV-vis-NIR transient absorption spectroscopy (λexc = 535 nm). Its S1 → Sn (n > 1) absorption bands appear with maxima at about λ ∼ 450 and 1220 nm. The short betanin S1 state lifetime (6.4 ps in water) is mainly determined by the efficient S1 → S0 radiationless relaxation, probably requiring a strong change in geometry, since the S1 lifetime grows to 27 ps in the more viscous ethylene glycol. The fluorescence quantum yield is very low (Φf ∼ 0.0007 in water), therefore this deactivation path is of minor importance. Other processes, such as S1 → T1 intersystem crossing or photoproduct formation, are virtually absent, since full S0 ← S1 ground state recovery is observed within tens of picoseconds after photoexcitation. The observed fast light-to-heat conversion in the absence of triplet excited state formation supports the idea that betanin is a photoprotector in vivo.

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Section: Introductionmentioning

confidence: 99%

Time-resolved spectroscopy of the singlet excited state of betanin in aqueous and alcoholic solutions

Wendel

Niziński

Tuwalska

et al. 2015

Phys. Chem. Chem. Phys.

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“…Aiming at the comparison between the proposed systems, an integral of overlapping was estimated (R) between the absorption of the methylene blue (ABS PS ) and the emission of the irradiation equipment (E EQUIP ) (equation 1), according to the method proposed by Bonacin et al 31 (1)…”

Section: Acquisition Of Irradiance Spectra and Measurementsmentioning

confidence: 99%

“…27 In recent years, several publications point out to the use of LED as a source of irradiation to satisfactorily promote the excitement of photosensitizers. [28][29][30][31] However, the present work aims at comparing and demonstrating advantages in the use of high intensity LED, in detriment to conventional LED, aside from providing guidelines for constructing an irradiation equipment based on LED arrays. Conventional colored 3 and 5 mm LED, widely found on the market, normally operate under a forward current of 20 mA, and have decreased rates of luminous emission (normally not exceeding 5,000 mcd).…”

Section: Introductionmentioning

confidence: 99%

A comparative study of irradiation systems for photoinactivation of microorganisms

Paula¹,

Santos²,

Menezes³

et al. 2010

J. Braz. Chem. Soc.

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Estudou-se a construção de sistemas de LED aplicados a processos de fotosensitização. Visando à obtenção de dispositivos mais eficientes avaliou-se a aplicação de LED de alta potência (HPLED), que apresenta maior fluxo fotônico, tendendo a excitar uma maior fração de moléculas. Foram descritos detalhes de construção de 3 diferentes sistemas de irradiação completamente distintos (lâmpada halógena filtrada, LED convencional, HPLED), utilizando azul de metileno como fotosensitizador. A comparação entre a eficiência de cada equipamento foi realizada através da cinética de fotooxidação de 1,3-Diphenylisobenzofuran e inativação de Staphylococcus aureus. A emissão de luz de cada equipamento, sobreposta à absorção do fotosensitizador, também se mostrou um importante parâmetro na estimativa da eficiência dos equipamentos. Foi observada uma inibição bacteriana superior a 99% para concentrações de 5 × 10 -6 mol dm -3 de fotosensitizador, no sistema que emprega HPLED. Os equipamentos baseados em LED, apresentaram resultados satisfatórios além de baixo custo e simples montagem.The construction of LED systems applied to photosensitization processes was studied. Aiming to obtain more efficient devices it was evaluated the use of high intensity LED (HPLED), that present greater photonic flux, tending to excite a greater fraction of molecules. Construction details for 3 different irradiation systems were described (filtered halogen bulbs, conventional LED, HPLED), using methylene blue as a photosensitizer. A comparison between the efficiency of the equipments was carried out through the kinetics of photooxidation of 1,3-Diphenylisobenzofuran and Staphylococcus aureus photoinactivation. The overlap between the light emited from each equipment and the photosensitizer absorption, was also an important parameter in estimating the efficiency of the equipment. Bacterial inhibition higher than 99% for concentrations of 5 × 10 -6 mol dm -3 of the photosensitizer was observed, in the system that uses HPLED. The equipments based on LED showed satisfactory results, besides their low cost and simple to assembling. Keywords: high power LED, Staphylococcus aureus, methylene blue, irradiation systems IntroductionPhotodynamic Inactivation (PDI) 1 or Photodynamic Antimicrobial Chemotherapy (PACT) 2 is the name of a process, derived from Photodynamic Therapy, that causes the death of microorganisms under the action of visible light and a specific drug, also called photosensitizer. 3 The electronic excitation of the photosensitizer in the presence of oxygen implies in the generation of a large number of reactive oxygen species (ROS), as for example, singlet oxygen, 4,5 in a process known as photosensitization.Since 1976, the oxidative action of singlet oxygen and other ROS on tumor cells has been reported in the medical and scientific communities. 5,6 Around the world, several research results have been published on the use of photosensitization to fight diseases caused by fungi, viruses, bacteria and yeasts. 3,5,[7][8][9][10][11] Among the photos...

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“…This pigment has a short-lived S 1 (p,p*) state (6.4 ps) (6,7) and processes such as photoproduct formation and S 1 ?T 1 intersystem crossing have been reported to be virtually absent (6). Although betanin cannot be used to produce singlet oxygen, its catechol moiety reacts with 1 O 2 allowing the convenient colorimetric detection of this reactive oxygen species (8,9). Due to its photoredox properties and binding strength of its carboxylic acid groups with metal oxides, for example, TiO 2 and ZnO, betanin has been used for the development of dye-sensitized solar cells and photocatalytic hydrogen production (10)(11)(12)(13)(14)(15)(16)(17).…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Mechanism of Hydrolysis of Betanin

Esteves

Pinheiro

Pioli

et al. 2018

Photochem & Photobiology

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Betanin (betanidin 5-O-β-D-glucoside) is a water-soluble plant pigment used as a color additive in food, drugs and cosmetic products. Despite its sensitivity to light and heat, betanin maintains appreciable tinctorial strength in low acidic and neutral conditions, where the color of other plant pigments, such as anthocyanins, quickly fades. However, betanin is an iminium natural product that experiences acid- and base-catalyzed hydrolysis to form the fairly stable betalamic acid and cyclo-DOPA-5-O-β-D-glucoside. Here, we show that the decomposition of betanin in aqueous phosphate solution pH 2-11 is subject to general base catalysis by hydrogen phosphate ion and intramolecular general acid and base catalysis, providing new insights on the mechanism of betanin hydrolysis. UV/Vis absorption spectrophotometry, H NMR spectroscopy and mass spectrometry were used to investigate product formation. Furthermore, theoretical calculations support the hypothesis that the nitrogen atom of the tetrahydropyridine ring of betanin is doubly protonated, as observed for structurally simpler amino dicarboxylic acids. Our results contribute to the study of betanin and other pigments belonging to the class of betalains and to deepen the knowledge on the chemical properties of imino acids as well as on iminium-catalyzed modifications of carbonyl compounds in water.

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Singlet oxygen quantum yields (Φd) in water using beetroot extract and an array of LEDs

Cited by 41 publications

References 24 publications

Time-resolved spectroscopy of the singlet excited state of betanin in aqueous and alcoholic solutions

Time-resolved spectroscopy of the singlet excited state of betanin in aqueous and alcoholic solutions

A comparative study of irradiation systems for photoinactivation of microorganisms

Revisiting the Mechanism of Hydrolysis of Betanin

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